The present invention generally relates to electrosurgical systems and methods for ablating, severing, contracting, or otherwise modifying target tissues or organs. The invention relates more particularly to electrosurgical apparatus and methods for coagulating a tissue or organ and for ablating the coagulated tissue or organ via molecular dissociation of tissue components. The present invention further relates to electrosurgical methods and apparatus for clamping a target tissue or blood vessel prior to coagulating and severing the tissue or blood vessel.
Conventional electrosurgical instruments and techniques are widely used in surgical procedures because they generally reduce patient bleeding and trauma associated with cutting operations, as compared with mechanical cutting and the like. Conventional electrosurgical procedures may be classified as operating in monopolar or bipolar mode. Monopolar techniques rely on external grounding of the patient, where the surgical device defines only a single electrode pole. Bipolar devices have two electrodes for the application of current between their surfaces. Conventional electrosurgical devices and procedures, however, suffer from a number of disadvantages. For example, conventional electrosurgical cutting devices typically operate by creating a voltage difference between the active electrode and the target tissue, causing an electrical arc to form across the physical gap between the electrode and the tissue. At the point of contact of the electric arcs with the tissue, rapid tissue heating occurs due to high current density between the electrode and the tissue. This high current density causes cellular fluids to rapidly vaporize into steam, thereby producing a “cutting effect” along the pathway of localized tissue heating. Thus, the tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue.
Further, monopolar electrosurgical devices generally direct electric current along a defined path from the exposed or active electrode through the patient's body to the return electrode, the latter externally attached to a suitable location on the patient. This creates the potential danger that the electric current will flow through undefined paths in the patient's body, thereby increasing the risk of unwanted electrical stimulation to portions of the patient's body. In addition, since the defined path through the patient's body has a relatively high electrical impedance, large voltage differences must typically be applied between the return and active electrodes in order to generate a current suitable for ablation or cutting of the target tissue. This current, however, may inadvertently flow along body paths having less impedance than the defined electrical path, which will substantially increase the current flowing through these paths, possibly causing damage to or destroying surrounding tissue.
Bipolar electrosurgical devices have an inherent advantage over monopolar devices because the return current path does not flow through the patient. In bipolar electrosurgical devices, both the active and return electrode are typically exposed so that both electrodes may contact tissue, thereby providing a return current path from the active to the return electrode through the tissue. One drawback with this configuration, however, is that the return electrode may cause tissue desiccation or destruction at its contact point with the patient's tissue. In addition, the active and return electrodes are typically positioned close together to ensure that the return current flows directly from the active to the return electrode. The close proximity of these electrodes generates the danger that the current will short across the electrodes, possibly impairing the electrical control system and/or damaging or destroying surrounding tissue.
In addition, conventional electrosurgical methods are generally ineffective for ablating certain types of tissue, and in certain types of environments within the body. For example, loose or elastic connective tissue, such as the synovial tissue in joints, is extremely difficult (if not impossible) to remove with conventional electrosurgical instruments because the flexible tissue tends to move away from the instrument when it is brought against this tissue. Since conventional techniques rely mainly on conducting current through the tissue, they are not effective when the instrument cannot be brought adjacent to, or in contact with, the elastic tissue for a sufficient period of time to energize the electrode and conduct current through the tissue.
There is a need for a general-purpose electrosurgical apparatus adapted for the precise removal or modification of a target tissue or organ at a specific location, wherein the target tissue or organ can be ablated, severed, resected, contracted, and/or coagulated, with minimal, or no, collateral tissue damage. The instant invention provides such an apparatus and related methods, wherein the apparatus includes at least one moveable electrode, and at least a portion of the target tissue or organ may be clamped between an active electrode and a return electrode prior to coagulation of the tissue or organ. Following coagulation, the coagulated tissue or organ may be ablated or severed.